1. Field of the Invention
This invention relates generally to heat sealing apparatus and more particularly to an improved impulse heat sealing station for sealing polymeric medical vials in tandem after filling with a medicament.
2. General Background
Manually operated heat sealing apparatus such as the Virtrod(trademark) have been in use for many years and have been adapted for use as medical vial sealing apparatus. However, such apparatus are considered archaic by today""s standards. While spare parts and technical support are still available from some companies, such as TechnaSeal(trademark), improved automated heat sealing machines have been developed to increase production demands. However, it is recognized that these older model vertical, special impulse heat sealing machines still play a vital role in today""s medical labs where medications can be produced and packaged in relatively small quantities on site. As production requirements increase in such labs a heavy demand is placed on these older types of heat sealing machines. There comes a point where it is no longer economical to expand the capacity of the machines or maintain the equipment with spare parts, which continue to increase in cost, as originally designed. Expanding the number of vials per load or increasing vial material thickness exerts excessive strain on the toggles and reduces sealing quality due to inadequate heat distribution, resulting in higher maintenance cost and poor quality products. In most such machines like the Virtrod(trademark) vertical vial sealer, sealing is achieved by simply bringing a movable heater head into contact with a stationary heater head. The polymeric material is thus pinched between the heads and heat is applied by an electrical heat strip running the length of the heads. The individual vials are held in racks of 4 or 8. The manually operated machines generally utilize a single over-center toggle lever to move the movable heater head into contact with the stationary head. The heat cycle is then timed to provide sufficient melting of the polymeric vial material and thus produce an effective seal However, as production requirements increase, the base units remains the same and longer heater heads are provided with higher wattage heater strips to accommodate longer racks of up to 14 vials. The single toggle operation then becomes over stressed and the toggle linkage becomes loose, causing misalignments of the heater bars, and allows for insufficient pressure on some of the vials, especially at the outer ends, thereby causing some vials to burn while others fail to make an effective seal. Such excessive heat causes the heater strips to have hot spots resulting in early failure. The longer heater bars are heavier, thereby requiring more torque to lift the movable bar, requiring operators to use both hands. Since no provision is made to shield the movable heater bar or provide a second handle, operators often receive severe burns. Further, since both hands are often used to operate the movable bars, it becomes more difficult to manipulate the movable head and hold the vial rack in position relative to the stationary heater head. No provision is made to hold the heavier movable heater heads in the up or open position while removing and replacing the vial racks, thereby resulting in more personnel injury due to burns. No provision is made to insure heater head alignment or to accommodate different thicknesses of vial polymeric materials. No provision is made to insure the proper pressure is placed on each vial to insure a quality seal. Polymeric vials are often produced in multi-cavity molds. When the vials are removed from such molds they are linked to each other by a relatively heavy web in groups or sets. It has been found that removing these webs takes time and excessive handling. In some cases, where sets of heat sealed packets are required, they are filled in the horizontal position or on a continuous feed system. In any case hand operated or manual sealing systems usually use only individual vials. Therefore, provisions need to be made to use the groups or sets, as produced by the vials manufacturing process, instead of handling the vials individually. This speeds up the filling and heat sealing process as well. However, it becomes necessary to provide precision racks and sealing head members with very efficient heat transfer capability to handle the groups in tandem.
No provision is made for non technical personnel to make repairs to this type of equipment. Simply replacing a heat strip is a major operation which often requires great dexterity due to the spring tensioning apparatus and procedure.
The prior art heater bars usually consist of a steel rectangular bar having a hole running lengthwise therethrough and tapped to receive water fittings. The bar is fitted at each end with a recessed terminal block composed of a micarta block with a stem portion extending from one side and tapped to receive a small screw on the opposite side. The terminal blocks are biased towards each end of the heater bar by a small spring imposed over the stem portion. The heater band is fitted with a pig tail wire at each end, soldered to the band at one end with a jack plug at the other. The band is then attached to the terminal connectors by compressing the two terminal blocks within the recesses in the heater block, thereby overcoming their bias and securing the heater band in place by the small screws mentioned above. This procedure requires more than two hands to accomplish and the heater bands often become loose relative to the micarta terminal blocks and burn the micarta resulting in premature failure. Teflon cloth strips are placed on either side of the heater bands and retained in place by elongated Teflon clamping strips, heat being dissipated throughout the heater bar as a function of its cross sectional area. Obviously, a better method is needed for replacing and protecting the heater bands and providing a more even distribution of heat.
Therefore, it behooves the industry to redesign the machines from time to time to improve their efficiency and thus improve their reliability, economics, and production capacity.
It is therefore an object of the this invention to provide a familiar but improved vertical, impulse heat sealing machine having a more substantial mechanical operating linkage for easier operation and more even distribution of pressure over the movable heater bars.
A further object is to provide a safer operation by providing insulated handles and locking bars.
Another object is to provide improved alignment between the moving and stationary heater bars and improve heat distribution along the bars.
Still another object is to reduce weight, improve replaceability, reduce maintenance and operating cost, improve handling efficiency, and maximize quality.
An improved vertical, vial, impulse heat sealing apparatus, the improvements including a light weight, precision milled frame with interchangability of component parts and increased structural strength, a more positive toggle system that eliminates misalignments allowing more stringent tolerances, a safety lock system to prevent operating personnel injury, improved stability and leverage efficiency, improved heat distribution, modular precision components for improved interchangability, improved terminal connector materials and method of heater band installation, improved connector-wire routing for improved heater bar replacement, provisions for precision shim plates specially adapted for use with proprietary vials in three tandem units of five vials each, specially designed precision vial holders, and an alternate embodiment providing a pneumatic conversion package for automatic operation and improved safety.